Abstract
We evaluated two osmotic adjustment substances (glycine betaine (GB) and glycine (G) and a combination of both glycine + glycine betaine (G + GB) using two modes of application; irrigation and foliar sprays with Dracaena sanderiana plants. The plants were grown in containers and subjected to two levels of NaCl concentrations (2.0 and 7.5 dS m−1) over 8 weeks. Growth, pigment concentrations, and physiological parameters were assessed at the end of the trial. The foliar application of GB resulted in most optimal plant growth and biomass production in the presence of NaCl. The chlorophyll and carotenoid concentrations showed different trends depending on the osmotic adjustment substance applied and the mode of application. Stomatal density and dimensions varied considerably with respect to the osmotic adjustment substance supplied. The concentration of soluble sugars in leaves did not show a clear trend under the different treatments assessed. The exogenous application of G resulted in the highest concentration of free proline and proteins in leaves. The antioxidant capacity in leaves increased with both osmotic adjustment substances, and both means of application, under low and high saline conditions. We concluded that the foliar application of GB can be recommended in order to achieve cost-effective growth of D. sanderiana under saline conditions.
Highlights
Salinity is an abiotic stress that causes sterile fields and reduces plant growth and yield [1] affecting an area of approximately 830 to 950 million hectares at a worldwide level [2]
Total leaf area decreased under increasing NaCl concentrations, and irrigation as the method of application resulted in the lowest total leaf area in plants treated without the use of any osmotic adjustment substance
The increase in plant height may be ascribed to the amelioration of salt damages in photosynthesis due to the exogenous application of glycine betaine (GB), and the positive effects of this osmotic adjustment substance may result in a higher synthesis of photosynthetic assimilates that are translocated to actively growing and expanding parts of plants promoting the growth
Summary
Salinity is an abiotic stress that causes sterile fields and reduces plant growth and yield [1] affecting an area of approximately 830 to 950 million hectares at a worldwide level [2]. Salinization causes a reduction in the productivity of crops, valued at as much as US $12 billion [4]. Plants grown in saline environments suffer osmotic stress and ion toxicity, which significantly reduce membrane porosity, growth rates, and yield [5]. The low rate of cell wall development and the reduction in growth are related to the osmotic stress caused by saline conditions in plants. The ionic stress comprises of a nutrient imbalance and a decrease in the photosynthetic apparatus in plants grown under saline environments [6]
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